Thermal pressure in erg/cm³ of the circumstellar medium at the same time as Figs. 3–5. This plot shows how the thermal pressure supporting the shell from the O-star side disappears at a larger distance (blue arrow). The shell still feels the ram pressure from the LBV star wind, which pushes it ahead, but without a counter force from the other side it is no longer compressed and starts to expand under its own internal pressure. This plot also shows how the O-star wind forms bowshocks around the individual deformations in the downstream region.